Computerized traffic control apparatus

ABSTRACT

Disclosed is a computerized apparatus for controlling the flow of vehicular traffic through a network of intersections. Detectors in proximity to selected intersections generate electrical signals representative of the commencement and termination of vehicle presence. One or more field preprocessors receive these signals and responsively generate secondary signals representative of vehicle count and speed. These secondary signals are transmitted to a computer which analyzes them and responsively generates control signals which are transmitted to and govern the sequential operation of traffic signal heads at the controlled intersections.

United States Patent Martin et al.

[ Nov. 18, 1975 COMPUTERIZED TRAFFIC CONTROL OTHER PUBLICATIONS APPAR ATUS Tonik, A. B., Development of Executive Routines, in [75] Inventors: Daniel T. Martin, Houston; Morton p ps c f pros 1967 FJCC), VOL 31 pp A. Serrell, Seabrook; Herbert C. 401402 NOV, 14.1 19 7 Cleman, Houston; Donald Gazis; D. c. et al., Def. Pub. Search Copy of Serial COOP", Houston; R0be" KHOX, No. 379,673, filed 914197l, Def. Pub. No. Seabrook; Curtis L. Barnfield, T920913 Houston, all of Tex.; Robert J. Walmchus Bammore Primary Examiner-R. Stephen Dildine, Jr. [73] Assignee: TRW Inc., Redondo Beach, Calif. 2 g Z k i T Z g t Filed: Feb. 1974 ep en J oun a pan erry mar o [21] App]. No.: 444,933 [57] ABSTRACT Related US. Application Data Disclosed is a computerized apparatus for controlling the flow of vehicular traffic through a network of in- [63] 5553; 1 :5 of May 1971 tersections. Detectors in proximity to selected intersections generate electrical signals representative of [52] CL 235/150 340/35. 340/36. the commencement and termination of vehicle pres- 340/172 ence. One or more field preprocessors receive these [51] hm 2 /48 signals and responsively generate secondary signals [58] Field of 340/ representative of vehicle count and speed. These sec- 2 1 ondary signals are transmitted to a computer which analyzes them and responsively generates control sig- [561 References Cited nals which are transmitted to and govern the sequenh d t th t ll d UNITED STATES PATENTS 212233;? of traffic signal ea 5 a e con ro e 3,533,086 10/1970 Goetz 444/1 3,828,307 8/1974 Hungerford 340/35 21 Clalms, 91 Drawing Flgures O O CONTROLLER COMMALD 16 I CONTROLLER STATUS I: FACKEM III I l l 7 [Elk-I 1 l I I DATA l DISC I DATA BASE I PARAMETERS I I I CHG1 XCHGO I i D 2 9 ONPOP I ET I l E I X 5 BACKGROUND I UTI L LKYPROTI I PRINTX*I L RADX I IOEX I DUMP I US. Patent Nov. 18,1975 Sheet 1 of 70 3,920,967

US. Patent Nov. 18, 1975 Sheet 2 of 70 3,920,967

CONTROLLER COMMAND CONTROLLER STATUS DATA MOPT

0 PACKEM DATA BASE DISC -L -PAiA-METERS J T T T UTlL SYMBO L XCHG l BAC KGROUN D QZDOmOmmOm DUMP \OEX

INVENTOR.

HERBERT C. COLEMAN BY RADX PRI NTX KYPROC FIG. 4

US. Patent Nov. 18, 1975 Sheet 3 of 70 3,920,967

I START SYSTEM START UP I ROUTINE LOAD ALL FOREG ROUND TASKS FROM THE RAD DETERMINE FIRST ADDRESS NOT USED BY FOREGROUND OR BACKGROUND ALLOT SPACE FOR TABLE OF ADDRESSES C OiA ITAUN I C ATTIONS .I 5 A PARAMETERS A SET UP TO USE REMAINING CORE AS BLOCKING BUFFERS LOAD ADDRESS TABLE FOR ON-- LINE COMMUNICATION PARAMETERS GET RUN TIME FROM SECOND WORD OF EACH FOREGROUND TASK AND ENTER IN SCHEDULE TABLE I NV EN TOR.

HERBERT C- COLEMAN US. Patent Nov. 18,1975 Sheet4of70 3,920,967

MAKE ENTRY IN SCHEDULE TABLE FOR CIU ROUTINE ARM AND ENABLE I/O AND EXTERN INTERRUPTS SEN D SETUP MESSAGE TO TELETYPEWRITER TRANSMIT INITIAL MESSAGE TO CIU SET TIMER FOR 350 ms.

ENTER DATA SWITCH SET ALL INTERRUPTS RECEIVED ISSUE ALARM MESSAGE AND ABO RT INVENTOR. HERBERT C- COLEMAN US. Patent Nov. 18, 1975 Fig 50 Sheet 5 of 70 SEND SYSTEM MESSAGE TO TELETYPEWRITER TRIGGER CALL IDLE ROUTINE ISSUE TASK MESSAGE TIME-O UT ABORT SYSTEM INTERRUPT TO ACTIVATE FIRST FO REG RO UND TASK ENTER IDLE ROUTINE S A ENTERED WHEN COUNTER 4 0 INTERRUPT r OCCURS SAVE REGISTER BLOCK I FOREGROUND TASK SCHEDULER 1s A SET FOREGROU ND FOREGROUND TASK ACTIVE ACTIVE FLAG ENTER NEXT FO REG RO UND TASK U.S. Patent Fig.7

BUILD LINKAGE TAB LE CALL ENTER IDLE ROUTINE Fig.8

Nov. 18, 1975 Sheet 6 of 70 I START SAVE REGISTERS GET REQ UESTER TASK I. D.

FG OR 86 WAS REQUEST TO EXECUTE A SYMBIONT LOADER FOREGROUND AND BACKGROUND EXIT ROUTINE BACKGROUND TASK AND SYMBIONT SCHEDULER ENTER REQUEST INQUEUE TABLE REQUEST TO RUN PRINT SYMBI ONT RETURN TO INTERRUPTED PROGRAM INVENTOR.

HERBERT C. COLEMAN U.S. Patent CIU COMMUNICATION ROUTINE Fig.9

Nov. 18, 1975 LOAD THE Cl U READ/WRITE ADDRESS REGISTERS SET ALL CIU INTERRUPT FLAGS RETURN HALT ALL FigIO Sheet 7 of 70 COMMAND SECTION ENTERED ON THE ENTER OccURANcE OF EXTERNAL INTRPS. 60, 61, AND 62. I v DETERMINE INTERRUPT NO. AND CLEAR FLAG INTERRUPT SECTION YES NO' RETURN TO INTERRUPTED PROGRAM ENTER I FAULT'TRAP ROUTINE DETERMINE FAULT NUMBER EDIT NUMBER TO ERROR MESSAGE SEND MESSAGE TO gag, TELETYPEWRITER INVENTOR.

HERBERT c. COLEMAN US. Patent Nov. 18, 1975 DAY CLOCK ROUTINE Fiqll ENTER Sheet 8 of 70 ENTERED ON THE OCCURAN CE OF COUNTER 3 O INTERRUPT (EVERY 1/32 OF A SECOND) YES RESET VT 32 ADD ONE TO TIME OF DAY IS IT MIDNIGHT RESET TIME OF DAY TO ZERO RETURN TO INTERRUPTED PROGRAM INVENTOR.

HERBERT C- COLEMAN U.S. Patent Nov. 18, 1975 She et90f70 3,920,967

L ENTER IDLE ROUTINE ANY UPDATE BACKGROUND SCHEDULE TASKS IN TAB LE QUEUE SETUP LINKAGE AND REQUEST TSKZiSikEL Fig. l2

YES ASK LOADED ENTER BACKGROUND TASK ENTER CAL 4 PROCESSOR SAVE REGISTERS AND PSD DETERMINE TYPE 0 F 1/0 REQUESTED y INVENTOR. ESR SPRI T HERBERT c. COLEMAN US. Patent Nov. 18, 1975 GO TO H/S PAPER TAPE HANDLER IS REQUEST FOR H/S PAPER TAPE QUEUE REQUEST AND RETURN ASR INTERRUPT ROUTINE Fl (3. I5 DECREMENT QUEUE COUNT FETCH FUNCTION WORD REQUEST FOR THE LINE PRINTER EXIT THROUGH l/O INTERRUPT RETURN FETCH NExT I REQUEST Z EL FROM UPWARD QUEUE SET R5= 3 Sheet 10 of 70 ASR HANDLER Fig. l4

GO TO LINE PRINTER HANDLER CLEAR LINE (HALT |/0 oN AS R) I QUEUE REQUEST SET AND BUSY RETURN FLAG SET R5 BUILD n/o DOUBLE WORD SEND I/O COMMAN D TO ASR EXIT THROUGH NO I/O INTERRUPT RETURN YES U.S. Patent Nov. 18, 1975 TYPE MANUAL MESSAG E PUT I IN INPUT BUFFER CARD READER HANDLER EXIT THROUGH IOEX RETURN INTERRUPT SECTION Fig. I68

ENTER Sheet 11 of 70 FETCH EOA PARAMETER BUILD l/O DOUBLE WORD SEND READ COMMAND WAS EOA REQUESTED READ SECTION Fig-I6A THIS ROUTINE IS 7 ENTERED WHEN AN I/O INTERRUPT IS RECEIVED FROM THE CARD READER BRANCH AND I LINK TO USER'S EOA ROUTINE (USES R5) EXIT THROUGH INTERRUPT RETURN INVENTOR. HERBERT C. COLEMAN U.S. Patent Nov. 18, 1975 Sheet 12 of 70 3,920,967

' TAPE HANDLER FETCH USER'S FUNCTION Fl T 7 BUILD l/O DOUBLE THIS ROUTINE IS WORD ENTERED WHEN AN INTERRUPT IS RECEIVED FROM THE MIOP T SAVE EXIT REGISTERS INTERRUPT THROUGH ROUTINE AND IOEx PSD RETURN ACKNOW- FT 9- T8 GO TO APPROPRIATE INTERRUPT ROUTINE HALT SET SET FLAG 2 FLAG I T/O ON TTY INVENTOR.

HERBERT c. COLEMAN GO TO U.S. Patent Nov. 18, 1975 IOEX RETURN ROUTINE Fig.|9

CL'EAR FLAG T BRANCH TO ROUTINE REQUESTING CONTROL Sheat 13 of 70 FLAG 2 WAS EOA REQUESTED BRANCH AND LINK TO REQUESTING ROUTINE ALL l/O INTERRUPT ROUTINES RETURN HERE SEND INPUT REQUEST TO ASR KEYBOARD Z ALL l/O SERVI'CE CALLS RETURN INHIBIT HERE INTERRUPTS RESTORE REGISTERS AND INVENTOR. PSD HERBERT c. COLEMAN ENTER q LINE PRINTER BUFFER ROUTINE GET BYTE COUNT O F MESSAGE FigZO THERE S ENOUGH SPACE YE FoR THIS MESSAGE DUMP BUFFER TO LINE PRINTER RAD BUFFER ROUTINE I ENTER NEW BUFFER sAvE LOAD PoINT BUILD COMPUTE No. WORDS 52%;? SETUP IAI-IIEISSSAGE TO INTERcEPT g MESSAGE PRINT I/o INTERRUPT ENTER CONTROL woRD IN REQUEST A CORE BUFFER BUFFER ENTER READ AOF A A ESSAGE BLOCK PRINT TO BUFFER THIS BUFFER ADD I RETURN COUNT THIS BUFFER U.S. Patent Nov. 18,1975 Sheet 15 of 70 3,920,967

THIS POINT IS THIS POINT IS ENTERED WHEN ENTERED AFTER AN INTERRUPT A PRINT BLOCK IS RECEIVED FROM IS READ FROM THE THE LINE PRINTER RAD.

SUBTRACT ONE FROM EN BLOCK COUNT SET I LINE PRINTER RETURN BUFFER ROUTlNE FOR PUT LOAD (CONTINUED) IOEx POINT FOR RETURN THIS ROUTINE IN R7 PUT LOAD POINT FOR GET LINE THIS ROUTINE COUNT IN R7 THIS BLOCK EXIT AND RELEASE PI 1;. 2! B THIS ROUTINE READ A NEW BLOCK CL' EED Y ,NVENTOR HERBERT C- COLEMAN US. Patent Nov. 18, 1975 LINE PRINTER BUFFER ROUTINE (CONTINUED) Fig-2K3 SET COMMAND FOR NO FORMAT CONTROL Sheet 16 of 70 SAVE REGISTERS R0 R2 SUBTRACT O NE FROM LINE COUNT GET CONTROL WORD FOR PRINT LINE REQUEST FOR FORMAT CONTROL SET COMMAND FOR FORMAT CONTROL BUILD l/O COMMAND SEND COMMAND TO PRINT LINE I RETURN 1N VEN TOR.

HERBERT C. COLEMAN US. Patent Nov. 18,1975 Sheet 17 of 70 3,920,967

RAD HANTDLER START GET FUN CTiON WORD UN PACK Fig. 22A g g LOAD REQUEST ISSUE ALARM MESSAGE ABORT SYSTEM SET R0 STATUS SET BUSY/NOT- BUSY RETURN GEES) INVENTOR.

HERBERT C- COLEMAN US. Patent Nov. 18, 1975 RAD HANDLER (CONTINUED) YES CLEAR STATUS FOR THIS FILE SET RETURN FLAG 0 REQUEST FOR READ OR WRITE SET EOA PARAMETER FOR THIS FILE SET RETURN FLAG BIT Sheet 18 of 70 INCREMENT BUSY COUNT THIS FILE SET EOA PARAMETER FOR THIS FILE SET BUSY FLAG Fig. 225

SET RAD SEEK ADDRESS PLACE REQUEST IN QUEUE RETURN USER INVENTOR.

HERBERT C. COLEMAN US. Patent Nov. 18, 1975 RAD HANDLER (CONTINUED) SET SECTOR COUNT TO ONE Shegt 19 0f 70 GET ITEM COUNT YES I COUNT REQUEST FOR READ OR WRITE IT A WORD REQUEST FOR BACKSPACE FIgZZC HERBERT C- COLEMAN 

1. An on-line, real-time traffic control apparatus for optimizing the flow of traffic between a plurality of intersections in a controlled network, said apparatus comprising: at least one automated detector means in proximity to each of selected ones of the intersections, each of said detector means adapted to generate, in response to the proximate presence of a vehicle, an electrical signal pulse, the commencement of which indicates the commencement of the vehicle presence and the termination Of which indicates the termination of the vehicle presence; at least one signal head in proximity to each of the intersections, said signal head adapted to successively display traffic flow directing lights; controller means adapted to control the operation of said signal heads; electronic computer means; means for electrical communication between said detector means and said computer means and between said computer means and said controller means, said communication means including signal processor means adapted to receive the signal pulses from a plurality of said detector means and to generate, in response to said signal pulses, an encoded binary electrical signal representing both the total number of signal pulses received by said processor means during a specified time span, and the duration of each, said total number indicative of vehicle count and each of said durations indicative of the speed of a vehicle in proximity to one of said detectors; said computer means being adapted to receive said encoded binary electrical signals from said processor means and, based thereupon, to generate necessary command electrical signals for said controller means, said command signals transmitted to said controller means through said communication means.
 2. The apparatus as recited in claim 1 wherein said signal processor means is adapted to respond to signal pulse discontinuities.
 3. The apparatus as recited in claim 2 wherein said discontinuities comprise signal pulse leading edges.
 4. The apparatus as recited in claim 2 wherein said discontinuities comprise signal pulse trailing edges.
 5. The apparatus as recited in claim 1, wherein said electronic computer means comprises: a. foreground computation means adapted to receive said encoded binary electrical signals from said processor means and, based thereupon, to generate necessary command electrical signals for said controllers, said command signals transmitted to said controllers through said communication means, b. background computation means in mutual electrical data signal communication with said foreground means, said background means adapted, in response to data from said foreground means, to generate a plurality of electrical data signals together representing an optimized pattern of commands for those of said controllers which control the operation of those said signal heads in proximity with said selected ones of the intersections, and c. executive operational means adapted to schedule the operation and the mutual interaction of said foreground means and background means.
 6. The apparatus as recited in claim 5, wherein said executive operational means comprises: electronic computer means for clocking an interval of time known as an execution cycle, which is defined as the sum of time allotted for completion of all foreground programs: electronic computer means for generating a program interrupt at the completion of an execution cycle; electronic computer means in response to said program interrupt for: stopping execution of a background program so as to perserve the background program environment, and executing the next and succeeding foreground programs in queue; electronic computer means for reactivating the interrupted background program and executing the next background program in queue at the completion of execution of all foreground programs; and electronic computer means for cyclically repeating above.
 7. The apparatus as recited in claim 5, wherein said foreground computation means includes apparatus for converting, in real time, speed and count data into relevant traffic parameters comprising: electronic computer means for constructing and updating a vehicle position/speed/direction matrix; electronic computer means for propagating vehicle counts at the measured speeds through a representation of a system of streets comprising the traffic control network; and electronic computer means for calculAting link input and output volume, number of stops, stop delay time, queue length, and travel time.
 8. The apparatus as recited in claim 7, wherein said means for constructing and updating said vehicle position/speed/direction matrix comprises: electronic computer means for constructing each column of said matrix to correspond to one-directional links within said network; electronic computer means for constructing the row elements of a specific column to correspond to fixed travel time units along said link; and electronic computer means for defining surveillance pointers corresponding to specific ingress or egress points along the link with respect to matrix elements where count data is to be entered, summed, modified or deleted.
 9. The apparatus as recited in claim 8, wherein said means for propagating vehicle counts at the measured speeds through a representation of a system of streets comprising the traffic control network comprises: electronic computer means for adjusting the relative positions of said surveillance pointers with respect to said matrix elements in unit travel time increments to account for variation in speed between surveillance points; and electronic computer means for decrementing the starting row number in a circular fashion for a preselected group of rows and columns within said matrix as each unit travel time elapses to advance unimpeded traffic forward in time and distance.
 10. The apparatus as recited in claim 9, wherein said means for calculating link input and output volume, number of stops, stop delay time, queue length and travel time comprises: electronic computer means for defining a set of surveillance pointers for each link; electronic computer means for summing and differencing input and output counts in each propagation time interval; electronic computer means for computing stops and delays from propagated vehicle counts and current signal light status; electronic computer means for computing queue length from said input and output count difference; and electronic computer means for summing said queue length each propagation time interval to determine travel time.
 11. The apparatus as recited in claim 7, further including: electronic computer means for computing signal phase termination times for minor intersections, said minor intersections located between major intersections and having minimal instrumentation using a pressure function.
 12. The apparatus as recited in claim 7, further including: electronic computer means for computing additional required measures of effectiveness from a basic set of surveillance parameters; electronic computer means for arranging said set of surveillance parameters in summary tables; and electronic computer means for normalizing surveillance count data by differencing and zeroing to prevent storage cell overflow.
 13. The apparatus as recited in claim 5, wherein said foreground computation means includes apparatus for optimally calculating and implementing splits at each intersection on a cycle-by-cycle basis within the constraint of maintaining the network progression comprising: electronic computer means for calculating the required effective green time for each signalized approach; electronic computer means for computing a first difference between the network cycle length and the maximum sum of green time required for each street at an intersection; electronic computer means for apportioning said first difference between each street based on the ratio of effective green times between any adjacent streets in said intersection; electronic computer means for calculating a new split based on said apportionment of total green time per street; and electronic computer means for optimally implementing the difference between the new split and the old split for each signalized approach.
 14. The apparatus as recited in claim 13, wherein the means for calculating the required effective green timE for each signalized approach comprises: electronic computer means for averaging the traffic volume over n cycles through each signalized approach to an intersection, whether left turn or straight through; electronic computer means for calculating the effective green time required to service the average volume in accordance with the following formula: tG V . HD/n where tG is the effective green time V is the average volume HD is the discharge headway per lane and n is the number of lanes per signalized approach; and electronic computer means for performing the first two steps for each signalized approach at said intersection.
 15. The apparatus as recited in claim 13, wherein the means for computing a first difference between the network cycle length and the maximum sum of green time required for each street and intersection comprises: electronic computer means for summing the green times per conflicting signal movements on each street; electronic computer means for summing the maximum green time for each street based on said sums of the green times per conflicting signal movements; and electronic computer means for computing said first difference between the network cycle length and said sum of maximum green times for each street.
 16. The apparatus as recited in claim 15, wherein the means for apportioning said first difference between each street based on the ratio of effective green times between any adjacent streets in said intersection comprises: electronic computer means for calculating the ratio of effective green time per street by dividing said sum of green times per conflicting signal movements by said sum of the maximum green times for each street; electronic computer means for calculating the split per street as follows: multiplying said ratio of effective green times per street by said first difference; adding said sum of the green time per conflicting signal movement; and electronic computer means for repeating the above two steps for each street in said intersection.
 17. The apparatus as recited in claim 16, further including: electronic computer means for comparing said new split with a preselected minimum value; and electronic computer means for adjusting said new split to be equal to said minimum value if said new split is less than said minimum value.
 18. The apparatus as recited in claim 5, wherein said background computation means includes apparatus for calculating optimum traffic signal settings for a traffic control network, in real time, including breaking down said network into subnetworks, optimizing each subnetwork, and interfacing each subnetwork wherein the means for optimizing each subnetwork comprises: electronic computer means for selecting a signal cycle range; electronic computer means for determining whether or not to reoptimize; electronic computer means for playing a series of Monte Carlo games for each signal cycle and using a gradient search technique to determine the optimum signal offsets for minimum delay and stops; and electronic computer means for determining the optimum signal cycle and corresponding offsets.
 19. The apparatus as recited in claim 18, wherein said background computation means further includes: electronic computer means for constructing a link weighting matrix, and electronic computer means for triangularizing and inverting said weighting matrix.
 20. The apparatus as recited in claim 18, wherein said apparatus is adapted to minimize the following function with respect to intersection offsets:
 21. The apparatus as recited in claim 18, wherein said apparatus is adapted to employ the following 